The conventional photodetecting device comprises a photodetector, a flexible printed wiring board for transmitting the output from the photodetector and a metallic substrate for supporting the photodetector and the flexible printed wiring board.
For example, FIGS. 1A and 1B illustrate a first conventional photodetecting device. FIG. 1A is a plan view of the device and FIG. 1B is a side view of the same.
In these figures, 110 denotes a metallic substrate, one surface of which serves as the surface joined to an optical head (not shown). On this surface, an insulating layer 111 is formed, on which a first land portion 112 and a second land portion 113 are formed.
Here, in order to prevent the interference between the optical head and the first and second land portions 112, 113, a predetermined interval is provided between the first land portion 112 and the second land portion 113, which are interconnected by means of a wiring pattern 114.
A photodetector 120 is mounted on the first land portion 112, and a flexible printed wiring board 130 is connected to the second land portion 113. The photodetector 120 has a light receiving surface at a top surface thereof.
Further, FIGS. 2A, 2B and 2C illustrate a second conventional photodetecting device. FIG. 2A is a plan view of the device, FIG. 2B is a side view of the same and FIG. 2C is a bottom view of the same.
In these figures, 210 denotes a metallic substrate, one surface of which serves as the surface joined to an optical head (not shown). On both surfaces of the substrate, an insulating layer 211 is formed. On the insulating layer 211 formed on the one surface of the metallic substrate 210 a first land portion 212 is formed. A photodetector 220 having a light receiving surface at a top surface thereof is mounted on the first land portion 212.
Further, on the insulating layer 211 formed on the other surface of the metallic substrate 210, a second land portion 213 is formed, and a flexible printed wiring board 230 is connected to the second land portion 213. The first land portion 212 and the second land portion 213 are interconnected by means of a through hole 214.
However, in the foregoing first and second conventional photodetecting devices, since the photodetectors 120, 220 are mounted on the insulating layers 111, 211 with which the optical head is in contact, a considerable constraint is posed on the position and size of the first land portions 112, 212 in order to improve the fit of the optical head on the device and prevent the electrical interruption such as short-circuit with the result that the photodetectors 120, 220 and the flexible printed wiring boards 130, 230 cannot be interconnected with a simple arrangement.
Further, in the first conventional photodetecting device, since the photodetector 120 and the flexible printed wiring board 130 are disposed on the surface with which the optical head is in contact, it is necessary to prevent the interference between the optical head and the flexible printed wiring board 130 during joining the former to the device.
As a result, an interval should be provided between the photodetector 120 and the flexible printed wiring board 130 to interconnect them by means of the wiring pattern 114 with the result that the area of the metallic substrate 110 is increased and the entire device is made greater.
On the other hand, in the second conventional photodetecting device, since the photodetector 220 and the flexible printed wiring board 230 are mounted on the metallic substrate 210 at a side distinct from each other, it is necessary to form the through hole 214 to make an interconnection between those.
However, in the interconnection by the through hole 214, a certain limit is posed in narrowing the distance between the adjacent first land portions 212 or the adjacent second land portions 213, and the arrangement of the device becomes complicated.
Incidentally, in Japanese Utility Model Application Laid-open No. 4-62507, a photodetecting device is proposed in which a through hole adapted for allowing the light to pass through is formed at the central portion of a substrate which has a resilient arm portion at its end portion, and a photodetector is mounted on the substrate at a position corresponding to the through hole, the resilient arm portion being fixed to an optical head by means of a screw, so that the photodetector is made movable in the direction of the optical axis by the adjustment of the screw.
However, in this photodetecting device, since the photodetector is mounted on the substrate and connected to a land portion without bending its lead portion which extends along the surface of the substrate, if the substrate is formed with metal, then the distance between the lead portion and the metallic portion of the substrate which is exposed at the inner wall portion of the through hole is so close that the electrical interruption such as short-circuit is caused.